A straight wire of diameter `0.5 mm` carrying a current of `1 A` is replaced by another wire of `1 mm` diameter carrying the same current. The strength of magnetic field far away is

Options

A. Twice the earlier value
B. Half of the earlier value
C. Quarter of its earlier value
D. Unchanged

Answer

D

Explanation

Since , `B = (mu_(0) I)/(2pi r)`
`r to` is the distance from the wire ,
`therefore` B is independent of radius of wire .